The Callet (http://www.thecallet.com) merges your iPhone with your wallet into an all-in-one product. The US$19.99 case/wallet utilizes the concept of a phone cover with accessible pockets.
The Callet is made from a Gel-Polymer and sports slit pockets to hold your cash and cards. It works with the iPhone 3G/3GS and iPhone 4 and comes in pink, blue, black and white.